1. Field of the Invention
The present invention relates to a high-speed WPAN (Wireless Personal Area Network) based on IEEE (Institute of Electrical and Electronics Engineers) 802.15.3 using an Ultra Wide Band (UWB) frequency. More particularly, the present invention relates to a high-speed WPAN capable of extending a service area so that communication between devices located in different pico-nets can be enabled.
2. Description of the Related Art
Typically, wireless communication technologies that use an Ultra Wide Band (UWB) frequency can transmit communications at a distance of about 10 m˜1 km when using a frequency band somewhere between 3.1 GHz to 10.6 GHz. For the past 40 years, the wireless communication technologies that used the UWB have been military wireless communication technologies in the US DOD (United States-Department of Defense). Recently, the FCC (Federal Communications Commission) opened the UWB frequency to the private sector.
Typically, the wireless communication technologies using the UWB frequency are often very high-speed wireless data transmission technologies based on the UWB of several GHz. In addition, these technologies typically have the characteristics of a high data rate (e.g., 500 Mbps˜1 Gbps), and low electric power (e.g., 1/100 of the electric power required for a mobile phone and a wireless LAN (Local Area Network)) when compared with existing IEEE 802.11 (Institute of Electrical and Electronics Engineers) and Bluetooth technologies. The wireless communication technologies operating in the UWB frequency range can be used in various fields, such as personal area networks that connect to computer systems, and peripheral devices. In addition, the operating frequency is also used by home appliances, for example, a very high-speed wireless Internet in a local area (e.g., an average distance of 10 m˜20 m and a maximum distance of 100 m). UWB frequencies are used for “through-the-wall” radars for detection of objects behind walls of buildings, high-precision positioning and geolocation systems, vehicle collision avoidance sensors, mine detectors, loss prevention systems, detectors for detecting objects inside human bodies, etc.
IEEE 802.15.3 high-speed WPAN (Wireless Personal Area Network) standards have been proposed in terms presuming that wireless communication technologies in this filed will communicate using UWB frequencies. In terms of IEEE 802 standard, IEEE 802.15.1 is a working group for standardizing Bluetooth specifications, and IEEE 802.11 is a working group for standardizing wireless LANs. A working group for IEEE 802.15.3 is exploring the high-speed WPAN standardizations utilizing UWB frequencies.
As well-known PAN (Personal Area Network) technology, Bluetooth has now reached the stage of commercialization. The Bluetooth technology has been recently adopted and commercialized in a lot of products. IEEE 802.11 wireless LANs have been completely standardized, although it is true that periodically the standards are revised in accordance with changes in technology, innovations, etc. The above-described networks mostly use a frequency band of 2.4 GHz (e.g., an ISM (Industrial, Scientific and Medical) radio band), and are used as a PAN solution within the communication distance of 10 m.
IEEE 802.15.3 working groups include TG1 (Task Group 1), TG2 and TG3. The TG1 is conducting the standardization of Bluetooth specifications. The TG2 is analyzing technologies for facilitating coexistence of Bluetooth products and existing wireless LANs. As a group for standardizing high-data-rate PAN solutions, the TG3 is currently studying a transmission scheme for implementing a data rate of 55 Mbps or above.
FIG. 1 illustrates an exemplary pico-net formed between devices located in an IEEE 802.15.3 high-speed WPAN. As shown in FIG. 1, the pico-net forming the high-speed WPAN includes a plurality of communication devices 10, 12, 14, 16 and 18. Here, the pico-net is a unit of a network providing communication service in an independent high-speed WPAN.
Among the devices shown in FIG. 1, the device 10 acts as a PNC (Pico-Net Coordinator). The PNC device 10 manages communications of the devices located in the pico-net using beacon messages for synchronizing its own device with the first through fourth devices 12, 14, 16 and 18 respectively connected thereto. Furthermore, the PNC device 10 also performs an operation for controlling QoS (Quality of Service), a power save mode and a pico-net access.
An IEEE 802.15.3 device capable of acting as the PNC can form one pico-net. A procedure for forming a pico-net by the PNC-capable device is as follows:
The PNC device 10 searches for at least one channel to initiate the pico-net operation by selecting one of the channels not currently in use, and by broadcasting a beacon frame through the selected channel. In response to the broadcasted beacon frame, the devices 12, 14, 16 and 18 carry out a communication channel setup operation. At this time, the PNC device 10 allocates IDs (Identifiers or Identities) corresponding to the devices 12, 14, 16 and 18.
When an arbitrary device desires to join an already-formed pico-net, an arbitrary device performs an association procedure. In other words, the arbitrary device moving within transmission range of the pico-net from an external area requests that the PNC device 10 to connect its own device to the already-formed pico-net. In response to the request, the PNC device 10 allocates a single device ID usable in the pico-net to the arbitrary device making the request.
Through the aforementioned procedure, the pico-net is formed as shown in FIG. 1. When the devices 12, 14, 16 and 18 desires to transmit data, the devices 12, 14, 16 and 18 request that the PNC device 10 also transmits data. In response to the data transmission requests from the devices 12, 14, 16 and 18, the PNC device 10 allocates timeslots for enabling data communications to the devices 12, 14, 16 and 18 by using the beacon frame. Consequently, each of the devices 12, 14, 16 and 18 performs a data transmission operation during a time corresponding to an allocated timeslot.
On the other hand, where an arbitrary device desires to terminate a communication operation within the pico-net or where the PNC device 10 desires to release a communication connection with the arbitrary device, a disassociation procedure between the PNC device 10 and the arbitrary device is performed. Thus, the PNC device 10 deletes information of the registered arbitrary device through the pico-net disassociation procedure.
Conventionally, the high-speed WPAN is a small-sized network for physically providing communication service within an approximately 10 m radius. As the high-speed WPAN capable of providing wireless service of 100 Mbps or above based on the wireless communication technology using the UWB frequencies has been developed, there still exists a need in the art to extend the service area to beyond the approximately 10 m radius that is the current limit.
Since transmission outputs are limited to −41.3 dBm or below (e.g., a frequency band of 3.1 GHz˜10.6 GHz) so that interference associated with an existing frequency band can be minimized, there still exists a problem in that the physical service area is limited to within the approximately 10 m radius, despite the fact that wireless communications in the high-speed WPAN utilize the UWB frequencies for wireless communications.
Communications between high-speed WPANs that are separate from each other cannot be supported by the IEEE 802.15.3 protocol. In other words, one PNC (Pico-net Coordinator) device is located in one pico-net, and the PNC device is responsible only for communications between devices within the same pico-net. However, the PNC device cannot communicate with a PNC device located in another pico-net.
The pico-net formed between the PNC device 10 and the devices 12, 14, 16 and 18 shown in FIG. 1 is classified into (1) an independent pico-net capable of independently allocating timeslots to the devices that are located within the pico-net, and (2) a dependent pico-net capable of distributing and allocating timeslots provided from a PNC device located outside the pico-net to the devices located in the pico-net. If at least one dependent pico-net is newly generated in an independent pico-net, then the independent pico-net is referred to as a “parent pico-net”, and the newly generated dependent pico-net is referred to as a “child pico-net” or “neighbor pico-net”. That is, the independent pico-net becomes the parent pico-net, and the dependent pico-net becomes the child pico-net. In this case, the child pico-net (or dependent pico-net) uses a common channel provided from the PNC device located in the parent pico-net.
Services between the parent and child pico-nets are provided using divided bandwidths. The result of using divide bandwidths is that a data transfer function cannot be performed between the parent and child pico-nets. Thus, communications between different pico-nets, i.e., communications between devices located in the different pico-nets, cannot be supported. To support the communication between the devices located in the different pico-nets, an IEEE 802.15.3 MAC (Media Access Control) bridge must be newly defined and implemented for all the devices. Furthermore, to support the communication between the devices located in the different pico-nets, a physically wired connection structure such as an optical fiber or a UTP (Unshielded Twisted Pair) cable must be configured, and an AP (Access Point) must be newly defined as in the high-speed WPAN.
FIG. 2 is a view illustrating the architecture of an exemplary high-speed WPAN using an optical fiber. It should be noted that the devices shown in FIG. 2 can use the communication protocol in the high-speed WPAN that is defined by IEEE 802.15.3.
As shown in FIG. 2, the conventional high-speed WPAN includes a central entity 20, a plurality of optical couplers 22, 24 and 26, a plurality of signal converters 31, 41 and 51 and a plurality of pico-nets 30, 40 and 50.
The central entity 20 performs a path setup function so that data can be switched and transmitted from the pico-nets 30, 40 and 50 to the destination devices. The plurality of optical couplers 22, 24 and 26 transmit the data from the central entity 20 to a connected path, and transmit the data from the pico-nets 30, 40 and 50 to the central entity 20.
The plurality of signal converters 31, 41 and 51 convert the optical signals that are received from the central entity 20 via the optical couplers 22, 24 and 26. The optical couplers connect the electrical signals and broadcast the electrical signals to corresponding pico-nets. Furthermore, the signal converters 31, 41 and 51 convert electrical signals received from devices of the pico-nets 30, 40 and 50 into optical signals, and then transmit the optical signals to the central entity 20.
The plurality of pico-nets 30, 40 and 50 include a plurality of PNC devices 32, 42 and 52 (one per pico-net), and a plurality of devices 33 to 37, 43 to 47 and 53 to 57 for transmitting data on the basis of timeslots allocated by the PNC devices 32, 42 and 52 that belong to the pico-nets 30, 40 and 50.
When communications are performed between the devices located in the different pico-nets in the high-speed WPAN architecture shown in FIG. 2, the central entity 20 receives data and transmits the received data to the destination pico-nets because the optical couplers 22, 24 and 26 cannot directly transmit the data to the destination pico-nets. The central entity 20 must have a PNC function for managing all the devices 33 to 37, 43 to 47 and 53 to 57 located in the respective pico-nets 30, 40 and 50 connected thereto through the optical fiber. Furthermore, there is a problem in that the central entity 20 must have a MAC bridge function necessary for switching and transmitting data from a source pico-net to a destination pico-net.
FIG. 3 is a table that lists data input and output states between the central entity 20 and the pico-net-A 30 in terms of the optical coupler-A 22 shown in FIG. 2. As shown in FIG. 3, it is assumed that “1”, “2” and “3” denote a path of the central entity 20, a path of the optical coupler-B 24 and a path of the pico-net-A 30, respectively, in terms of the optical coupler-A 22. Data inputted into the optical coupler-A 22 from the path of the central entity 20, i.e., the “1” path, are outputted to the “2” and “3” paths. Data input from the “2” path is output to the “1” path over the optical coupler-A 22, and data input from the “3” path is output to the “1” path over the optical coupler-A 22.
For example, when data is transmitted from the pico-net-C 50 to an arbitrary device located in the pico-net-B 40, a signal that has been opto-electrically converted by the signal converter-C 51 is not directly transmitted to the pico-net-B 40 over the optical coupler-C 26, but is transmitted to the central entity 20. The central entity 20 broadcasts the received signal to the pico-nets 30, 40 and 50 over the MAC bridge function. At this time, the devices 33 to 37, 43 to 47 and 53 to 57 located in the pico-nets 30, 40 and 50 analyze ID (Identifier or Identity) information of the data that is broadcast from the central entity 20 and then received from the signal converters 31, 41 and 51, and determine whether the received data corresponds to their own devices, respectively.
In order for data to be transmitted between different pico-nets as described above, the data must be transmitted to the central entity 20 and subsequently be transmitted to a destination pico-net. Thus, there is a drawback in that the conventional high-speed WPAN must perform additional operations involving the central entity.